This invention relates to a process for synthesizing mercaptans from alcohols and hydrogen sulfide. In particular, it relates to a novel catalyst for use in that process.
Mercaptans can be synthesized by reacting alcohols with hydrogen sulfide in the presence of a catalyst. Catalysts used for this reaction have included bases such as potassium hydroxide and transition metal oxides, such as K.sub.2 WO.sub.4, on an alumina substrate. These catalysts can produce selectivities as high as 95% for the conversion of methanol to methyl mercaptan, but conversions of higher molecular weight alcohols to mercaptans are substantially lower. Alcohol that is not converted to mercaptan is converted into undesired byproducts, such as alkenes, ethers, and sulfides; unreacted alcohol may also be present in the product mixture. Not only is this a waste of alcohol, but it is usually necessary to separate the desired mercaptan from these byproducts, which may be difficult since an azeotrope may exist between the alcohol and the mercaptan. This adds an additional expensive step to the production process.